Nanomaterials

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4 pages, 178 KiB

Open AccessEditorial

Catalysis by Metal-Oxide Nanostructures

by Sónia Alexandra Correia Carabineiro

Nanomaterials 2024, 14(5), 415; https://doi.org/10.3390/nano14050415 - 24 Feb 2024

Viewed by 806

Abstract

Catalysis is an important field dealing with innovation, sustainability, and materials science that has been witnessing remarkable advancements through nanotechnology [...] Full article

(This article belongs to the Special Issue Catalysis by Metal-Oxide Nanostructures)

Research

Jump to: Editorial, Review

17 pages, 5298 KiB

Open AccessArticle

Ni-Modified Ag/SiO₂ Catalysts for Selective Hydrogenation of Dimethyl Oxalate to Methyl Glycolate

by Shuai Cheng, Tao Meng, Dongsen Mao, Xiaoming Guo, Jun Yu and Zhen Ma

Nanomaterials 2022, 12(3), 407; https://doi.org/10.3390/nano12030407 - 26 Jan 2022

Cited by 11 | Viewed by 3137

Abstract

Ni-modified Ag/SiO₂ catalysts containing 0~3 wt.% Ni were obtained by impregnating Ni species onto Ag/SiO₂ followed by calcination and reduction. The catalysts’ performance in the hydrogenation of dimethyl oxalate (DMO) to methyl glycolate (MG) was tested. Ag-0.5%Ni/SiO₂ showed the highest [...] Read more.

Ni-modified Ag/SiO₂ catalysts containing 0~3 wt.% Ni were obtained by impregnating Ni species onto Ag/SiO₂ followed by calcination and reduction. The catalysts’ performance in the hydrogenation of dimethyl oxalate (DMO) to methyl glycolate (MG) was tested. Ag-0.5%Ni/SiO₂ showed the highest catalytic activity among these catalysts and exhibited excellent catalytic stability. The effects of the Ni content on the structure and surface chemical states of catalysts were investigated by XRF, N₂-sorption, XRD, TEM, EDX-mapping, FT-IR, H₂-TPR, UV–vis, and XPS. The better catalytic activity and stability of Ni-modified Ag/SiO₂ (versus Ag/SiO₂) are ascribed to the improved dispersion of active Ag species as well as the higher resistance to the growth of Ag particles due to the presence of Ni species. Full article

(This article belongs to the Special Issue Catalysis by Metal-Oxide Nanostructures)

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11 pages, 2125 KiB

Open AccessArticle

Hollow CoP/FeP₄ Heterostructural Nanorods Interwoven by CNT as a Highly Efficient Electrocatalyst for Oxygen Evolution Reactions

by Yanfang Liu, Yong Li, Qi Wu, Zhe Su, Bin Wang, Yuanfu Chen and Shifeng Wang

Nanomaterials 2021, 11(6), 1450; https://doi.org/10.3390/nano11061450 - 30 May 2021

Cited by 11 | Viewed by 3156

Abstract

Electrolysis of water to produce hydrogen is crucial for developing sustainable clean energy and protecting the environment. However, because of the multi-electron transfer in the oxygen evolution reaction (OER) process, the kinetics of the reaction is seriously hindered. To address this issue, we [...] Read more.

Electrolysis of water to produce hydrogen is crucial for developing sustainable clean energy and protecting the environment. However, because of the multi-electron transfer in the oxygen evolution reaction (OER) process, the kinetics of the reaction is seriously hindered. To address this issue, we designed and synthesized hollow CoP/FeP₄ heterostructural nanorods interwoven by carbon nanotubes (CoP/FeP₄@CNT) via a hydrothermal reaction and a phosphorization process. The CoP/FeP₄@CNT hybrid catalyst delivers prominent OER electrochemical performances: it displays a substantially smaller Tafel slope of 48.0 mV dec⁻¹ and a lower overpotential of 301 mV at 10 mA cm⁻², compared with an RuO₂ commercial catalyst; it also shows good stability over 20 h. The outstanding OER property is mainly attributed to the synergistic coupling between its unique CNT-interwoven hollow nanorod structure and the CoP/FeP₄ heterojunction, which can not only guarantee high conductivity and rich active sites, but also greatly facilitate the electron transfer, ion diffusion, and O₂ gas release and significantly enhance its electrocatalytic activity. This work offers a facile method to develop transition metal-based phosphide heterostructure electrocatalysts with a unique hierarchical nanostructure for high performance water oxidation. Full article

(This article belongs to the Special Issue Catalysis by Metal-Oxide Nanostructures)

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14 pages, 5521 KiB

Open AccessArticle

Catalytic Performance of a Magnetic Core-Shell Iron(II) C-Scorpionate under Unconventional Oxidation Conditions

by Inês A. S. Matias, Ana P. C. Ribeiro, Ana M. Ferraria, Ana M. Botelho do Rego and Luísa M. D. R. S. Martins

Nanomaterials 2020, 10(11), 2111; https://doi.org/10.3390/nano10112111 - 23 Oct 2020

Cited by 8 | Viewed by 2238

Abstract

For the first time, herein is reported the use of a magnetic core-shell support for a C-scorpionate metallic complex. The prepared hybrid material, that consists on the C-scorpionate iron(II) complex [FeCl₂{κ³-HC(pz)₃}] (pz, pyrazolyl) immobilized at magnetic core-shell [...] Read more.

For the first time, herein is reported the use of a magnetic core-shell support for a C-scorpionate metallic complex. The prepared hybrid material, that consists on the C-scorpionate iron(II) complex [FeCl₂{κ³-HC(pz)₃}] (pz, pyrazolyl) immobilized at magnetic core-shell particles (Fe₃O₄/TiO₂), was tested as catalyst for the oxidation of secondary alcohols using the model substrate 1-phenylethanol. Moreover, the application of alternative energy sources (e.g., ultrasounds, microwaves, mechanical or thermal) for the peroxidative alcohol oxidation using the magnetic heterogenized iron(II) scorpionate led to different/unusual outcomes that are presented and discussed. Full article

(This article belongs to the Special Issue Catalysis by Metal-Oxide Nanostructures)

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25 pages, 2916 KiB

Open AccessArticle

Development of Chitosan Functionalized Magnetic Nanoparticles with Bioactive Compounds

by Gordana Hojnik Podrepšek, Željko Knez and Maja Leitgeb

Nanomaterials 2020, 10(10), 1913; https://doi.org/10.3390/nano10101913 - 25 Sep 2020

Cited by 30 | Viewed by 3799

Abstract

In this study, magnetic maghemite nanoparticles, which belong to the group of metal oxides, were functionalized with chitosan, a non-toxic, hydrophilic, biocompatible, biodegradable biopolymer with anti-bacterial effects. This was done using different synthesis methods, and a comparison of the properties of the synthesized [...] Read more.

In this study, magnetic maghemite nanoparticles, which belong to the group of metal oxides, were functionalized with chitosan, a non-toxic, hydrophilic, biocompatible, biodegradable biopolymer with anti-bacterial effects. This was done using different synthesis methods, and a comparison of the properties of the synthesized chitosan functionalized maghemite nanoparticles was conducted. Characterization was performed using scanning electron microscopy (SEM) and vibrating sample magnetometry (VSM). Characterizations of size distribution were performed using dynamic light scattering (DLS) measurements and laser granulometry. A chitosan functionalization layer was confirmed using potentiometric titration on variously synthesized chitosan functionalized maghemite nanoparticles, which is important for further immobilization of bioactive compounds. Furthermore, after activation of chitosan functionalized maghemite nanoparticles with glutaraldehyde (GA) or pentaethylenehexamine (PEHA), immobilization studies of enzyme cholesterol oxidase (ChOx) and horseradish peroxidase (HRP) were conducted. Factors influencing the immobilization of enzymes, such as type and concentration of activating reagent, mass ratio between carrier and enzyme, immobilization time and enzyme concentration, were investigated. Briefly, microparticles made using the chitosan suspension cross-linking process (MC2) proved to be the most suitable for obtaining the highest activity of immobilized enzyme, and nanoparticles functionalized with chitosan using the covalent binding method (MC3) could compete with MC2 for their applications. Full article

(This article belongs to the Special Issue Catalysis by Metal-Oxide Nanostructures)

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12 pages, 4983 KiB

Open AccessArticle

Carbon Quantum Dots Modified (002) Oriented Bi₂O₂CO₃ Composites with Enhanced Photocatalytic Removal of Toluene in Air

by Junping Ding, Huanchun Wang, Yidong Luo, Yushuai Xu, Jinsheng Liu, Ruichu Lin, Yuchen Gao and Yuanhua Lin

Nanomaterials 2020, 10(9), 1795; https://doi.org/10.3390/nano10091795 - 9 Sep 2020

Cited by 18 | Viewed by 3259

Abstract

In work, (002) oriented flower-like Bi₂O₂CO₃(BOC) composites are synthesized by a facile chemical route and carbon quantum dots (CQDs) are modified on their surfaces through a hydrothermal method. The synthesized samples (CQD/BOC) are characterized by X-ray diffraction [...] Read more.

In work, (002) oriented flower-like Bi₂O₂CO₃(BOC) composites are synthesized by a facile chemical route and carbon quantum dots (CQDs) are modified on their surfaces through a hydrothermal method. The synthesized samples (CQD/BOC) are characterized by X-ray diffraction (XRD), SEM, X-ray photoelectron spectroscopy (XPS), UV-Vis diffuser reflectances (DRS), BET and TEM/HRTEM. The morphologies of CQD/BOC composites are the flower-like shapes, the irregular flaky structures and the fine spherical particles of CQDs attached. Photocatalytic performances were investigated in terms of removing gaseous toluene at a concentration of 94.3ppm in air, with the assistance of CQD/BOC under artificial irradiation. Our results show that CQDs modified (002) oriented Bi₂O₂CO₃ exhibits good photocatalytic activity for toluene decomposition, which can be attributed to the enhanced efficient charge separation. A certain ratio composite photocatalyst (BOC-CQD-15) shows a toluene removal rate of 96.62% in three hours, as well as great stability. CO₂ was verified to be the primary product. The oriented flower-like Bi₂O₂CO₃ with carbon quantum dots on the surface shows great potential in the field of solar driven air purification. Full article

(This article belongs to the Special Issue Catalysis by Metal-Oxide Nanostructures)

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24 pages, 2823 KiB

Open AccessArticle

Impact of Thermal Treatment of Nb₂O₅ on Its Performance in Glucose Dehydration to 5-Hydroxymethylfurfural in Water

by Katarzyna Morawa Eblagon, Anna Malaika, Karolina Ptaszynska, Manuel Fernando R. Pereira and José Luís Figueiredo

Nanomaterials 2020, 10(9), 1685; https://doi.org/10.3390/nano10091685 - 27 Aug 2020

Cited by 21 | Viewed by 3371

Abstract

The cascade dehydration of glucose to 5-hydroxymethylfurfural (HMF) was carried out in water over a series of Nb₂O₅ catalysts, which were derived from the thermal treatment of niobic acid at 300 and 550 °C, under air or inert atmosphere. Amorphous [...] Read more.

The cascade dehydration of glucose to 5-hydroxymethylfurfural (HMF) was carried out in water over a series of Nb₂O₅ catalysts, which were derived from the thermal treatment of niobic acid at 300 and 550 °C, under air or inert atmosphere. Amorphous niobic acid showed high surface area (366 m²/g) and large acidity (2.35 mmol/g). With increasing the temperature of the thermal treatment up to 550 °C, the amorphous Nb₂O₅ was gradually transformed into a pseudohexagonal phase, resulting in a decrease in surface area (27–39 m²/g) and total acidity (0.05–0.19 mmol/g). The catalysts’ performance in cascade dehydration of glucose realized in pure water was strongly influenced by the total acidity of these materials. A remarkable yield of 37% HMF in one-pot reaction in water was achieved using mesoporous amorphous niobium oxide prepared by thermal treatment of niobic acid at 300 °C in air. The best-performing catalyst displayed a total acidity lower than niobic acid (1.69 mmol/g) which afforded a correct balance between a high glucose conversion and limited further conversion of the target product to numerous polymers and humins. On the other hand, the treatment of niobic acid at 550 °C, independently of the atmosphere used during the sample preparation (i.e., air or N₂), resulted in Nb₂O₅ catalysts with a high ratio of Lewis to Brønsted acid sites and poor total acidity. These materials excelled at catalyzing the isomerization step in the tandem process. Full article

(This article belongs to the Special Issue Catalysis by Metal-Oxide Nanostructures)

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16 pages, 5209 KiB

Open AccessArticle

One Step Synthesis of Tetragonal-CuBi₂O₄/Amorphous-BiFeO₃ Heterojunction with Improved Charge Separation and Enhanced Photocatalytic Properties

by Fang Cai, Ting Zhang, Qiong Liu, Pengran Guo, Yongqian Lei, Yi Wang and Fuxian Wang

Nanomaterials 2020, 10(8), 1514; https://doi.org/10.3390/nano10081514 - 1 Aug 2020

Cited by 8 | Viewed by 3290

Abstract

Tetragonal CuBi₂O₄/amorphous BiFeO₃ (T-CBO/A-BFO) composites are prepared via a one-step solvothermal method at mild conditions. The T-CBO/A-BFO composites show expanded visible light absorption, suppressed charge recombination, and consequently improved photocatalytic activity than T-CBO or A-BFO alone. The T-CBO/A-BFO [...] Read more.

Tetragonal CuBi₂O₄/amorphous BiFeO₃ (T-CBO/A-BFO) composites are prepared via a one-step solvothermal method at mild conditions. The T-CBO/A-BFO composites show expanded visible light absorption, suppressed charge recombination, and consequently improved photocatalytic activity than T-CBO or A-BFO alone. The T-CBO/A-BFO with an optimal T-CBO to A-BFO ratio of 1:1 demonstrates the lowest photoluminescence signal and highest photocatalytic activity. It shows a removal rate of 78.3% for the photodegradation of methylene orange under visible light irradiation for 1 h. XPS test after the cycle test revealed the reduction of Bi³⁺ during the photocatalytic reaction. Moreover, the as prepared T-CBO/A-BFO show fundamentally higher photocatalytic activity than their calcinated counterparts. The one-step synthesis is completed within 30 min and does not require post annealing process, which may be easily applied for the fast and cost-effective preparation of photoactive metal oxide heterojunctions. Full article

(This article belongs to the Special Issue Catalysis by Metal-Oxide Nanostructures)

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11 pages, 1756 KiB

Open AccessArticle

Cationic Magnetite Nanoparticles for Increasing siRNA Hybridization Rates

by Artur Y. Prilepskii, Arseniy Y. Kalnin, Anna F. Fakhardo, Elizaveta I. Anastasova, Daria D. Nedorezova, Grigorii A. Antonov and Vladimir V. Vinogradov

Nanomaterials 2020, 10(6), 1018; https://doi.org/10.3390/nano10061018 - 27 May 2020

Cited by 5 | Viewed by 2318

Abstract

An investigation of the interaction principles of nucleic acids and nanoparticles is a priority for the development of theoretical and methodological approaches to creating bionanocomposite structures, which determines the area and boundaries of biomedical use of developed nanoscale devices. «Nucleic acid—magnetic nanoparticle» type [...] Read more.

An investigation of the interaction principles of nucleic acids and nanoparticles is a priority for the development of theoretical and methodological approaches to creating bionanocomposite structures, which determines the area and boundaries of biomedical use of developed nanoscale devices. «Nucleic acid—magnetic nanoparticle» type constructs are being developed to carry out the highly efficient detection of pathogens, create express systems for genotyping and sequencing, and detect siRNA. However, the data available on the impact of nanoparticles on the behavior of siRNA are insufficient. In this work, using nanoparticles of two classical oxides of inorganic chemistry (magnetite (Fe₃O₄) and silica (SiO₂) nanoparticles), and widely used gold nanoparticles, we show their effect on the rate of siRNA hybridization. It has been determined that magnetite nanoparticles with a positive charge on the surface increase the rate of siRNA hybridization, while negatively charged magnetite and silica nanoparticles, or positively charged gold nanoparticles, do not affect hybridization rates (HR). Full article

(This article belongs to the Special Issue Catalysis by Metal-Oxide Nanostructures)

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26 pages, 6383 KiB

Open AccessArticle

Effect of Gold Electronic State on the Catalytic Performance of Nano Gold Catalysts in n-Octanol Oxidation

by Ekaterina Pakrieva, Ekaterina Kolobova, Yulia Kotolevich, Laura Pascual, Sónia A. C. Carabineiro, Andrey N. Kharlanov, Daria Pichugina, Nadezhda Nikitina, Dmitrii German, Trino A. Zepeda Partida, Hugo J. Tiznado Vazquez, Mario H. Farías, Nina Bogdanchikova, Vicente Cortés Corberán and Alexey Pestryakov

Nanomaterials 2020, 10(5), 880; https://doi.org/10.3390/nano10050880 - 2 May 2020

Cited by 13 | Viewed by 3648

Abstract

This study aims to identify the role of the various electronic states of gold in the catalytic behavior of Au/M_xO_y/TiO₂ (where M_xO_y are Fe₂O₃ or MgO) for the liquid phase oxidation of [...] Read more.

This study aims to identify the role of the various electronic states of gold in the catalytic behavior of Au/M_xO_y/TiO₂ (where M_xO_y are Fe₂O₃ or MgO) for the liquid phase oxidation of n-octanol, under mild conditions. For this purpose, Au/M_xO_y/TiO₂ catalysts were prepared by deposition-precipitation with urea, varying the gold content (0.5 or 4 wt.%) and pretreatment conditions (H₂ or O₂), and characterized by low temperature nitrogen adsorption-desorption, X-ray powder diffraction (XRD), energy dispersive spectroscopy (EDX), scanning transmission electron microscopy-high angle annular dark field (STEM HAADF), diffuse reflectance Fourier transform infrared (DRIFT) spectroscopy of CO adsorption, temperature-programmable desorption (TPD) of ammonia and carbon dioxide, and X-ray photoelectron spectroscopy (XPS). Three states of gold were identified on the surface of the catalysts, Au⁰, Au¹⁺ and Au³⁺, and their ratio determined the catalysts performance. Based on a comparison of catalytic and spectroscopic results, it may be concluded that Au⁺ was the active site state, while Au⁰ had negative effect, due to a partial blocking of Au⁰ by solvent. Au³⁺ also inhibited the oxidation process, due to the strong adsorption of the solvent and/or water formed during the reaction. Density functional theory (DFT) simulations confirmed these suggestions. The dependence of selectivity on the ratio of Brønsted acid centers to Brønsted basic centers was revealed. Full article

(This article belongs to the Special Issue Catalysis by Metal-Oxide Nanostructures)

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26 pages, 8541 KiB

Open AccessArticle

Fitting Biochars and Activated Carbons from Residues of the Olive Oil Industry as Supports of Fe- Catalysts for the Heterogeneous Fenton-Like Treatment of Simulated Olive Mill Wastewater

by Bruno M. Esteves, Sergio Morales-Torres, Francisco J. Maldonado-Hódar and Luis M. Madeira

Nanomaterials 2020, 10(5), 876; https://doi.org/10.3390/nano10050876 - 1 May 2020

Cited by 29 | Viewed by 3678

Abstract

A series of biochars and activated carbons (ACs) was prepared combining carbonization and physical or chemical activation of cheap and abundant residues of the olive oil industry. These materials were used as Fe-support to develop low-cost catalysts for the heterogeneous Fenton-like oxidation of [...] Read more.

A series of biochars and activated carbons (ACs) was prepared combining carbonization and physical or chemical activation of cheap and abundant residues of the olive oil industry. These materials were used as Fe-support to develop low-cost catalysts for the heterogeneous Fenton-like oxidation of simulated olive mill wastewater (OMW), the highly pollutant effluent generated by this agroindustry. Commercial ACs were also used as reference. All catalysts prepared were extensively characterized and results related with their performances in the catalytic wet peroxide oxidation (CWPO). Results showed a linear relationship of the textural properties of the catalysts with the adsorptive and catalytic performance, as well as the preferential adsorption and degradation of some phenolic compounds (caffeic and gallic acids) by specific interactions with the catalysts’ surface. Despite the best performance of catalysts developed using commercial supports, those prepared from agro-industrial residues present some advantages, including a smaller catalyst deactivation by iron leaching. CWPO results show that catalysts from physically activated olive stones are the most promising materials, reaching total organic carbon and toxicity reductions of 35% and 60%, respectively, as well an efficient use of H₂O₂, comparable with those obtained using commercial supports. This approach showed that the optimized treatment of this type of residues will allow their integration in the circular economic process of the olive oil production. Full article

(This article belongs to the Special Issue Catalysis by Metal-Oxide Nanostructures)

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14 pages, 4861 KiB

Open AccessArticle

Investigation on Mn₃O₄ Coated Ru Nanoparticles for Partial Hydrogenation of Benzene towards Cyclohexene Production Using ZnSO₄, MnSO₄ and FeSO₄ as Reaction Additives

by Xingai Liu, Zhihao Chen, Haijie Sun, Lingxia Chen, Zhikun Peng and Zhongyi Liu

Nanomaterials 2020, 10(4), 809; https://doi.org/10.3390/nano10040809 - 23 Apr 2020

Cited by 4 | Viewed by 3430

Abstract

Mn₃O₄ coated Ru nanoparticles (Ru@Mn₃O₄) were synthesized via a precipitation-reduction-gel method. The prepared catalysts were evaluated for partial hydrogenation of benzene towards cyclohexene generation by applying ZnSO₄, MnSO₄ and FeSO₄ as reaction [...] Read more.

Mn₃O₄ coated Ru nanoparticles (Ru@Mn₃O₄) were synthesized via a precipitation-reduction-gel method. The prepared catalysts were evaluated for partial hydrogenation of benzene towards cyclohexene generation by applying ZnSO₄, MnSO₄ and FeSO₄ as reaction additives. The fresh and spent catalysts were thoroughly characterized by XRD, X ray fluorescence (XRF), XPS, TEM and N₂-physicalsorption in order to understand the promotion effect of Mn₃O₄ as the modifier as well as ZnSO₄, MnSO₄ and FeSO₄ as reaction additives. It was found that 72.0% of benzene conversion and 79.2% of cyclohexene selectivity was achieved after 25 min of reaction time over Ru@Mn₃O₄ with a molar ratio of Mn/Ru being 0.46. This can be rationalized in terms of the formed (Zn(OH)₂)₃(ZnSO₄)(H₂O)₃ on the Ru surface from the reaction between Mn₃O₄ and the added ZnSO₄. Furthermore, Fe²⁺ and Fe³⁺ compounds could be generated and adsorbed on the surface of Ru@Mn₃O₄ when FeSO₄ is applied as a reaction additive. The most electrons were transferred from Ru to Fe, resulting in that lowest benzene conversion of 1.5% and the highest cyclohexene selectivity of 92.2% after 25 min of catalytic experiment. On the other hand, by utilizing MnSO₄ as an additive, no electrons transfer was observed between Ru and Mn, which lead to the complete hydrogenation of benzene towards cyclohexane within 5 min. In comparison, moderate amount of electrons were transferred from Ru to Zn²⁺ in (Zn(OH)₂)₃(ZnSO₄)(H₂O)₃ when ZnSO₄ is used as a reaction additive, and the highest cyclohexene yield of 57.0% was obtained within 25 min of reaction time. Full article

(This article belongs to the Special Issue Catalysis by Metal-Oxide Nanostructures)

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23 pages, 4113 KiB

Open AccessArticle

Supported Gold Nanoparticles as Catalysts in Peroxidative and Aerobic Oxidation of 1-Phenylethanol under Mild Conditions

by Ekaterina Pakrieva, Ana P. C. Ribeiro, Ekaterina Kolobova, Luísa M. D. R. S. Martins, Sónia A. C. Carabineiro, Dmitrii German, Daria Pichugina, Ce Jiang, Armando J. L. Pombeiro, Nina Bogdanchikova, Vicente Cortés Corberán and Alexey Pestryakov

Nanomaterials 2020, 10(1), 151; https://doi.org/10.3390/nano10010151 - 15 Jan 2020

Cited by 9 | Viewed by 3815

Abstract

The efficiency of Au/TiO₂ based catalysts in 1-phenylethanol oxidation was investigated. The role of support modifiers (La₂O₃ or CeO₂), influence of gold loading (0.5% or 4%) and redox pretreatment atmosphere, catalyst recyclability, effect of oxidant: tert-butyl [...] Read more.

The efficiency of Au/TiO₂ based catalysts in 1-phenylethanol oxidation was investigated. The role of support modifiers (La₂O₃ or CeO₂), influence of gold loading (0.5% or 4%) and redox pretreatment atmosphere, catalyst recyclability, effect of oxidant: tert-butyl hydroperoxide (TBHP) or O₂, as well as the optimization of experimental parameters of the reaction conditions in the oxidation of this alcohol were studied and compared with previous studies on 1-octanol oxidation. Samples were characterized by temperature-programmed oxygen desorption (O₂-TPD) method. X-ray photoelectron spectroscopy (XPS) measurements were carried out for used catalysts to find out the reason for deactivation in 1-phenylethanol oxidation. The best catalytic characteristics were shown by catalysts modified with La₂O₃, regardless of the alcohol and the type of oxidant. When O₂ was used, the catalysts with 0.5% Au, after oxidative pretreatment, showed the highest activity in both reactions. The most active catalysts in 1-phenylethanol oxidation with TBHP were those with 4% Au and the H₂ treatment, while under the same reaction conditions, 0.5% Au and O₂ treatment were beneficial in 1-octanol oxidation. Despite the different chemical nature of the substrates, it seems likely that Au⁺(Au^δ+) act as the active sites in both oxidative reactions. Density functional theory (DFT) simulations confirmed that the gold cationic sites play an essential role in 1-phenylethanol adsorption. Full article

(This article belongs to the Special Issue Catalysis by Metal-Oxide Nanostructures)

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21 pages, 2626 KiB

Open AccessArticle

CO₂ Hydrogenation over Nanoceria-Supported Transition Metal Catalysts: Role of Ceria Morphology (Nanorods versus Nanocubes) and Active Phase Nature (Co versus Cu)

by Michalis Konsolakis, Maria Lykaki, Sofia Stefa, Sόnia A. C. Carabineiro, Georgios Varvoutis, Eleni Papista and Georgios E. Marnellos

Nanomaterials 2019, 9(12), 1739; https://doi.org/10.3390/nano9121739 - 6 Dec 2019

Cited by 49 | Viewed by 4871

Abstract

In this work we report on the combined impact of active phase nature (M: Co or Cu) and ceria nanoparticles support morphology (nanorods (NR) or nanocubes (NC)) on the physicochemical characteristics and CO₂ hydrogenation performance of M/CeO₂ composites at atmospheric pressure. [...] Read more.

In this work we report on the combined impact of active phase nature (M: Co or Cu) and ceria nanoparticles support morphology (nanorods (NR) or nanocubes (NC)) on the physicochemical characteristics and CO₂ hydrogenation performance of M/CeO₂ composites at atmospheric pressure. It was found that CO₂ conversion followed the order: Co/CeO₂ > Cu/CeO₂ > CeO₂, independently of the support morphology. Co/CeO₂ catalysts demonstrated the highest CO₂ conversion (92% at 450 °C), accompanied by 93% CH₄ selectivity. On the other hand, Cu/CeO₂ samples were very selective for CO production, exhibiting 52% CO₂ conversion and 95% CO selectivity at 380 °C. The results obtained in a wide range of H₂:CO₂ ratios (1–9) and temperatures (200–500 °C) are reaching in both cases the corresponding thermodynamic equilibrium conversions, revealing the superiority of Co- and Cu-based samples in methanation and reverse water-gas shift (rWGS) reactions, respectively. Moreover, samples supported on ceria nanocubes exhibited higher specific activity (µmol CO₂·m⁻²·s⁻¹) compared to samples of rod-like shape, disclosing the significant role of support morphology, besides that of metal nature (Co or Cu). Results are interpreted on the basis of different textural and redox properties of as-prepared samples in conjunction to the different impact of metal entity (Co or Cu) on CO₂ hydrogenation process. Full article

(This article belongs to the Special Issue Catalysis by Metal-Oxide Nanostructures)

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13 pages, 6269 KiB

Open AccessArticle

Facile Preparation of Pd/UiO-66-v for the Conversion of Furfuryl Alcohol to Tetrahydrofurfuryl Alcohol under Mild Conditions in Water

by Yanliang Yang, Dongsheng Deng, Dong Sui, Yanfu Xie, Dongmi Li and Ying Duan

Nanomaterials 2019, 9(12), 1698; https://doi.org/10.3390/nano9121698 - 28 Nov 2019

Cited by 17 | Viewed by 3661

Abstract

The hydrogenation of furan ring in the biomass-derived furans is of great importance for the conversion of biomass to valuable chemicals. Fabrication of high activity and selectivity catalyst for this hydrogenation under mild conditions was one of the focuses of this research. In [...] Read more.

The hydrogenation of furan ring in the biomass-derived furans is of great importance for the conversion of biomass to valuable chemicals. Fabrication of high activity and selectivity catalyst for this hydrogenation under mild conditions was one of the focuses of this research. In this manuscript, UiO-66-v, in which vinyl bonded to the benzene ring, was first prepared. Then, the uniformly distributed vinyl was used as the reductant for the preparation of Pd/UiO-66-v. The catalyst was characterized by X-ray diffraction, thermogravimetric, N₂ physical adsorption/desorption, X-ray photoelectron spectroscopy, scanning electron microscope, transmission electron microscopy, energy dispersive spectrometer elemental mappings, and inductively coupled plasma atomic emission spectroscopy to find the Pd/UiO-66-v had a narrow palladium nanoparticles size of 3–5 nm and maintained the structure and thermal stability of UiO-66-v. The Pd/UiO-66-v was used for the hydrogenation of furfuryl alcohol to tetrahydrofurfuryl alcohol in water. 99% conversion of furfuryl alcohol was obtained with 90% selectivity to tetrahydrofurfuryl alcohol after reacted at 0.5 MPa H₂, 303 K for 12 h. The Pd/UiO-66-v was proved to be effective for the hydrogenation of furan ring in furans and could be used for at least five times. Full article

(This article belongs to the Special Issue Catalysis by Metal-Oxide Nanostructures)

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17 pages, 6495 KiB

Open AccessArticle

Fabrication of Bimetal CuFe₂O₄ Oxide Redox-Active Nanocatalyst for Oxidation of Pinene to Renewable Aroma Oxygenates

by Lindokuhle S. Mdletshe, Peter R. Makgwane and Suprakas S. Ray

Nanomaterials 2019, 9(8), 1140; https://doi.org/10.3390/nano9081140 - 9 Aug 2019

Cited by 20 | Viewed by 4229

Abstract

This study report on the synthesis of spinel CuFe₂O₄ nanostructures by surfactant-assisted method. The catalysts were characterized by X-ray diffraction (XRD), laser Raman, transition electron microscope (TEM), scanning electron microscope (SEM), energy dispersive X-ray (EDX), hydrogen temperature programmed reduction (H [...] Read more.

This study report on the synthesis of spinel CuFe₂O₄ nanostructures by surfactant-assisted method. The catalysts were characterized by X-ray diffraction (XRD), laser Raman, transition electron microscope (TEM), scanning electron microscope (SEM), energy dispersive X-ray (EDX), hydrogen temperature programmed reduction (H₂-TPR), and Brunauer-Teller-Emmett-Teller (BET) surface area techniques. CuFe₂O₄ was active for pinene oxidation using tertiary butyl hydroperoxide (TBHP) to pinene oxide, verbenol, and verbenone aroma oxygenates. Under optimized reaction conditions, the spinel CuFe₂O₄ catalyst could afford 80% pinene conversion at a combined verbenol/verbenone selectivity of 76% within the reaction time of 20 h. The changes in catalyst synthesis solvent composition ratios induced significantly varying redox, phases, and textural structure features, which resulted in various catalytic enhancement effect. Characterization results showed the spinel CuFe₂O₄ catalyst possessing less than 5 wt% impurity phases, Cu(OH)₂, and CuO to afford the best catalytic performance. The CuFe₂O₄ catalyst was recyclable to up to five reaction cycles without loss of its activity. The recyclability of the bimetal CuFe₂O₄ oxide catalyst was simply rendered by use of an external magnet to separate it from the liquid solution. Full article

(This article belongs to the Special Issue Catalysis by Metal-Oxide Nanostructures)

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17 pages, 8412 KiB

Open AccessArticle

Removal of Phenolic Compounds from Water Using Copper Ferrite Nanosphere Composites as Fenton Catalysts

by Carlos Moreno-Castilla, María Victoria López-Ramón, María Ángeles Fontecha-Cámara, Miguel A. Álvarez and Lucía Mateus

Nanomaterials 2019, 9(6), 901; https://doi.org/10.3390/nano9060901 - 20 Jun 2019

Cited by 25 | Viewed by 5556

Abstract

Copper ferrites containing Cu⁺ ions can be highly active heterogeneous Fenton catalysts due to synergic effects between Fe and Cu ions. Therefore, a method of copper ferrite nanosphere (CFNS) synthesis was selected that also permits the formation of cuprite, obtaining a CFNS [...] Read more.

Copper ferrites containing Cu⁺ ions can be highly active heterogeneous Fenton catalysts due to synergic effects between Fe and Cu ions. Therefore, a method of copper ferrite nanosphere (CFNS) synthesis was selected that also permits the formation of cuprite, obtaining a CFNS composite that was subsequently calcined up to 400 °C. Composites were tested as Fenton catalysts in the mineralization of phenol (PHE), p-nitrophenol (PNP) and p-aminophenol (PAP). Catalysts were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and magnetic measurements. Degradation of all phenols was practically complete at 95% total organic carbon (TOC) removal. Catalytic activity increased in the order PHE < PNP < PAP and decreased when the calcination temperature was raised; this order depended on the electronic effects of the substituents of phenols. The as-prepared CFNS showed the highest catalytic activity due to the presence of cubic copper ferrite and cuprite. The Cu⁺ surface concentration decreased after calcination at 200 °C, diminishing the catalytic activity. Cuprite alone showed a lower activity than the CFNS composite and the homogeneous Fenton reaction had almost no influence on its overall activity. CFNS activity decreased with its reutilization due to the disappearance of the cuprite phase. Degradation pathways are proposed for the phenols. Full article

(This article belongs to the Special Issue Catalysis by Metal-Oxide Nanostructures)

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11 pages, 3450 KiB

Open AccessArticle

MoS₂ Coexisting in 1T and 2H Phases Synthesized by Common Hydrothermal Method for Hydrogen Evolution Reaction

by Yixin Yao, Kelong Ao, Pengfei Lv and Qufu Wei

Nanomaterials 2019, 9(6), 844; https://doi.org/10.3390/nano9060844 - 2 Jun 2019

Cited by 140 | Viewed by 9777

Abstract

Molybdenum disulfide has been one of the most studied hydrogen evolution catalyst materials in recent years, but its disadvantages, such as poor conductivity, hinder its further development. Here, we employ the common hydrothermal method, followed by an additional solvothermal method to construct an [...] Read more.

Molybdenum disulfide has been one of the most studied hydrogen evolution catalyst materials in recent years, but its disadvantages, such as poor conductivity, hinder its further development. Here, we employ the common hydrothermal method, followed by an additional solvothermal method to construct an uncommon molybdenum disulfide with two crystal forms of 1T and 2H to improve catalytic properties. The low overpotential (180 mV) and small Tafel slope (88 mV/dec) all indicated that molybdenum disulfide had favorable catalytic performance for hydrogen evolution. Further conjunctions revealed that the improvement of performance was probably related to the structural changes brought about by the 1T phase and the resulting sulfur vacancies, which could be used as a reference for the further application of MoS₂. Full article

(This article belongs to the Special Issue Catalysis by Metal-Oxide Nanostructures)

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15 pages, 4170 KiB

Open AccessArticle

Metal-Support Cooperative Effects in Au/VPO for the Aerobic Oxidation of Benzyl Alcohol to Benzyl Benzoate

by Sebastiano Campisi, Michele Ferri, Carine E. Chan-Thaw, Felipe J. Sanchez Trujillo, Davide Motta, Tommaso Tabanelli, Nikolaos Dimitratos and Alberto Villa

Nanomaterials 2019, 9(2), 299; https://doi.org/10.3390/nano9020299 - 20 Feb 2019

Cited by 10 | Viewed by 4247

Abstract

This paper studies the cooperative effect of Au nanoparticles deposited on vanadyl pyrophosphate oxide (VPO) in the liquid phase oxidation of benzyl alcohol. VPO was prepared using the classical method by thermally treating VOHPO₄·0.5H₂O precursor in reacting atmosphere at [...] Read more.

This paper studies the cooperative effect of Au nanoparticles deposited on vanadyl pyrophosphate oxide (VPO) in the liquid phase oxidation of benzyl alcohol. VPO was prepared using the classical method by thermally treating VOHPO₄·0.5H₂O precursor in reacting atmosphere at 420 °C for a period of 72 h. Au nanoparticles were deposited by incipient wetness method. The catalysts were characterized by means of XRD, TEM, XPS and Raman. The bulk VPO catalyst contains vanadyl pyrophosphate phase ((VO)₂P₂O₇), and a small amount of VOPO₄. The catalytic system exhibits a high activity in the base-free liquid phase oxidation of alcohols compared to Au on activated carbon, classic catalyst used for this type of reaction. Au/VPO showed a high peculiar selectivity to benzyl benzoate (76%), an important product used in the pharmaceutical and perfume industries. This behavior might be ascribed to the presence of strong acid sites of VPO, as determined by liquid phase titration. Stability tests performed on Au/VPO showed a deactivation of 10% after the first run, but a constant conversion along the following five cycles. This phenomenon can be attributed to the increase of mean Au particle size (from 19.1 to 23.4 nm) after recycling tests as well as the partial leaching of Au and V in the reaction media. Moreover, XRD evidenced a modification in the VPO structure with the partial formation of VOHPO₄·0.5H₂O phase. Full article

(This article belongs to the Special Issue Catalysis by Metal-Oxide Nanostructures)

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Review

Jump to: Editorial, Research

30 pages, 8474 KiB

Open AccessReview

Catalytic Methane Decomposition to Carbon Nanostructures and CO_x-Free Hydrogen: A Mini-Review

by Ahmed Gamal, Kamel Eid, Muftah H. El-Naas, Dharmesh Kumar and Anand Kumar

Nanomaterials 2021, 11(5), 1226; https://doi.org/10.3390/nano11051226 - 6 May 2021

Cited by 55 | Viewed by 5737

Abstract

Catalytic methane decomposition (CMD) is a highly promising approach for the rational production of relatively CO_x-free hydrogen and carbon nanostructures, which are both important in multidisciplinary catalytic applications, electronics, fuel cells, etc. Research on CMD has been expanding in recent years [...] Read more.

Catalytic methane decomposition (CMD) is a highly promising approach for the rational production of relatively CO_x-free hydrogen and carbon nanostructures, which are both important in multidisciplinary catalytic applications, electronics, fuel cells, etc. Research on CMD has been expanding in recent years with more than 2000 studies in the last five years alone. It is therefore a daunting task to provide a timely update on recent advances in the CMD process, related catalysis, kinetics, and reaction products. This mini-review emphasizes recent studies on the CMD process investigating self-standing/supported metal-based catalysts (e.g., Fe, Ni, Co, and Cu), metal oxide supports (e.g., SiO₂, Al₂O₃, and TiO₂), and carbon-based catalysts (e.g., carbon blacks, carbon nanotubes, and activated carbons) alongside their parameters supported with various examples, schematics, and comparison tables. In addition, the review examines the effect of a catalyst’s shape and composition on CMD activity, stability, and products. It also attempts to bridge the gap between research and practical utilization of the CMD process and its future prospects. Full article

(This article belongs to the Special Issue Catalysis by Metal-Oxide Nanostructures)

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